Arriving at Constantinople to oversee Constantius' burial, Julian immediately focused on domestic policy and began to greatly reform the Roman imperial government by reorganizing, streamlining, and reducing the bureaucracy.

Turning next to foreign policy, Julian saw the previously unchecked military incursions of Shapur II of Persia against the Eastern Roman provinces as posing the greatest external threat.

After many failed earlier attempts, the Persian king launched a more successful second campaign against the Romans and captured Amida in 359, controlling the headwaters of the Tigris and the entrance to Asia Minor from the east.

Seeing Julian successfully march into his dominions, Shapur ordered his governors to undertake a scorched earth policy until he reached the Sassanid capital, Ctesiphon, with the main Persian army.

However, Julian lacked the equipment to lay siege to the strongly fortified Ctesiphon, and the main Sassanid army, commanded by Shapur and far larger than the one just defeated, was closing in quickly.

[citation needed] Reluctantly, Julian agreed to retreat back along the Tigris and look for Procopius and the other half of his army that had failed to coordinate the double-pincers movement with him outside of Ctesiphon as had been planned.